You probably need to change the location of the music files for example to /mnt/media; the web_root location to /usr/local/share/mt-daapd/admin-root; the plugin directory to /usr/local/share/mt-daapd/plugins; the firefly database directory to for example /mnt/media; and the playlist directory to for example /etc/mt-daapd/mt-daapd.playlist. Check that all the directories you use actually exist on your installation. If you cannot access the Firefly web interface, check that the music file and web_root location exist, and remember Linux is case sensitive i.e. /mnt/media and /mnt/Media are different directories.

(allow any user to write to mt-daapd.conf to allow web interface to modify it)